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style="" data-v-aa0e2252><a class="outline-link" href="#_3-less安装（注意如果使用vscode无需安装less）" data-v-aa0e2252>3.Less安装（注意如果使用VSCode无需安装Less）</a><!----></li><li style="" data-v-aa0e2252><a class="outline-link" href="#_4-注释-comments" data-v-aa0e2252>4.注释(Comments)</a><!----></li><li style="" data-v-aa0e2252><a class="outline-link" href="#_5-变量-variables" data-v-aa0e2252>5.变量(Variables)</a><!----></li><li style="" data-v-aa0e2252><a class="outline-link" href="#_6-嵌套-nesting" data-v-aa0e2252>6.嵌套(Nesting)</a><!----></li><li style="" data-v-aa0e2252><a class="outline-link" href="#_7-混合-mixins" data-v-aa0e2252>7.混合(Mixins)</a><!----></li><li style="" data-v-aa0e2252><a class="outline-link" href="#_8-继承-extend" data-v-aa0e2252>8.继承(Extend)</a><!----></li><li style="" data-v-aa0e2252><a class="outline-link" href="#_10-函数（functions）" data-v-aa0e2252>10.函数（Functions）</a><!----></li><li style="" data-v-aa0e2252><a class="outline-link" href="#_11-导入（importing）" data-v-aa0e2252>11.导入（Importing）</a><!----></li><li style="" data-v-aa0e2252><a class="outline-link" href="#_12-导出" data-v-aa0e2252>12.导出</a><!----></li><!--]--></ul></nav></div><!--[--><!--[--><!--[--><div><a class="sponsors-aside-text" href="/">联系客服</a><img src="/images/qrcode.png"></div><!--]--><!--]--><!--]--><div class="VPCarbonAds" data-v-4fe9b7bd><img src="/logo.svg" alt="" srcset=""></div><!--[--><!--[--><!--[--><h1 class="tagline" data-v-3916b2f0><span class="accent" data-v-3916b2f0>Bin</span><br data-v-3916b2f0>QQ - 1974892005 </h1><!--]--><!--]--><!--]--></div></div><div class="content" data-v-4fe9b7bd><!--[--><!--]--><main data-v-4fe9b7bd><div style="position:relative;" class="vt-doc less" data-v-4fe9b7bd><div><h1 id="less基础" tabindex="-1">Less基础 <a class="header-anchor" href="#less基础" aria-hidden="true">#</a></h1><h2 id="_1-维护css的弊端" tabindex="-1">1.维护CSS的弊端 <a class="header-anchor" href="#_1-维护css的弊端" aria-hidden="true">#</a></h2><p>CSS 是一门非程序式语言，没有变量、函数、SCOPE（作用域）等概念。</p><ul><li>CSS 需要书写大量看似没有逻辑的代码，CSS 冗余度是比较高的</li><li>不方便维护及扩展，不利于复用</li><li>CSS 没有很好的计算能力</li><li>非前端开发工程师来讲，往往会因为缺少 CSS 编写经验而很难写出组织良好且易于维护的 CSS 代码项目</li></ul><h2 id="_2-less介绍" tabindex="-1">2.Less介绍 <a class="header-anchor" href="#_2-less介绍" aria-hidden="true">#</a></h2><p>Less（Leaner Style Sheets 的缩写）是一门 CSS 扩展语言，也称为 CSS 预处理器。</p><p>做为 CSS 的一种形式的扩展，它并没有减少 CSS 的功能，而是在现有的 CSS 语法上，为 CSS 加入程序式语言的特性。</p><p>它在 CSS 的语法基础上，引入了变量，Mixin（混入），运算以及函数等功能，大大简化了 CSS 的编写，并且降低了 CSS 的维护成本，就像它的名称所说的那样，Less 可以让我们用更少的代码做更多的事情。</p><p>Less 中文网址：<a href="https://less.bootcss.com/" target="_blank" rel="noopener noreferrer">Less 快速入门 | Less.js 中文文档 - Less 中文网 (bootcss.com)</a></p><p>常见的 CSS 预处理器：Sass、Less、Stylus</p><p>一句话：Less 是一门 CSS 预处理语言，它扩展了 CSS 的动态特性。</p><h2 id="_3-less安装（注意如果使用vscode无需安装less）" tabindex="-1">3.Less安装（注意如果使用VSCode无需安装Less） <a class="header-anchor" href="#_3-less安装（注意如果使用vscode无需安装less）" aria-hidden="true">#</a></h2><p><strong>用node运行Less</strong></p><ol><li>安装 node.js，可选择版本（8.0），网址：<a href="http://nodejs.cn/download/" target="_blank" rel="noopener noreferrer">http://nodejs.cn/download/</a></li><li>检查是否安装成功，使用 cmd 命令输入 <code>node -v</code> 查看版本即可</li><li>基于 node.js 在线安装 Less，使用 cmd 命令输入 <code>npm install -g less</code> 即可</li><li>检查是否安装成功，使用 cmd 命令 <code>lessc -v</code> 查看版本即可</li></ol><p><strong>vscode使用Less</strong></p><p>本质上，Less 包含一套自定义的语法及一个解析器，用户根据这些语法定义自己的样式规则，这些规则最终会通过解析器，编译生成对应的 CSS 文件。</p><p>所以，我们需要把我们的 Less 文件，编译生成为 CSS 文件，这样我们的 HTML 页面才能使用。</p><p>【VSCode Less 插件】</p><p>vscode 的 Easy LESS 插件</p><p>这个插件可以自动将<code>less</code>文件转义成<code>css</code>文件 <strong>关于配置</strong></p><p><img src="https://i0.hdslb.com/bfs/album/414fbd1d48b8bce8313ae5ddc66469d7b3548974.png" alt=""></p><p><strong>settings.json配置如下</strong></p><div class="language-json line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;">&quot;</span><span style="color:#C3E88D;">less.compile</span><span style="color:#89DDFF;">&quot;</span><span style="color:#A6ACCD;">: </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">        </span><span style="color:#89DDFF;">&quot;</span><span style="color:#C792EA;">compress</span><span style="color:#89DDFF;">&quot;</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">true,</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">// true =&gt; remove surplus whitespace</span></span>
<span class="line"><span style="color:#A6ACCD;">        </span><span style="color:#89DDFF;">&quot;</span><span style="color:#C792EA;">sourceMap</span><span style="color:#89DDFF;">&quot;</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">true,</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">// true =&gt; generate source maps (.css.map files)将浏览器审查元素中css代码在css文件中的位置改成对应的less文件中的位置</span></span>
<span class="line"><span style="color:#A6ACCD;">        </span><span style="color:#89DDFF;">&quot;</span><span style="color:#C792EA;">out</span><span style="color:#89DDFF;">&quot;</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">true</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">// false =&gt; DON&#39;T output .css files (overridable per-file, see below)生成对应的css文件</span></span>
<span class="line"><span style="color:#A6ACCD;">    </span><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div><p>只要保存一下 less 文件，会自动生成 CSS 文件。</p><h2 id="_4-注释-comments" tabindex="-1">4.注释(Comments) <a class="header-anchor" href="#_4-注释-comments" aria-hidden="true">#</a></h2><ul><li>多行注释保留</li><li>单行注释不被保留在编译生成的 CSS 中</li></ul><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#676E95;font-style:italic;">/* </span></span>
<span class="line"><span style="color:#676E95;font-style:italic;"> * 一个块注释</span></span>
<span class="line"><span style="color:#676E95;font-style:italic;"> * style comment! </span></span>
<span class="line"><span style="color:#676E95;font-style:italic;">*/</span></span>
<span class="line"></span>
<span class="line"><span style="color:#676E95;font-style:italic;">// 这一行被注释掉了！</span></span>
<span class="line"><span style="color:#FFCB6B;">div</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> red</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br></div></div><h2 id="_5-变量-variables" tabindex="-1">5.变量(Variables) <a class="header-anchor" href="#_5-变量-variables" aria-hidden="true">#</a></h2><p>变量是指没有固定值，可以改变的。因为我们 CSS 中的一些颜色和数值等经常使用。</p><p><code>@变量名: 值;</code></p><p>变量是指没有固定值，可以改变的。因为我们 CSS 中的一些颜色和数值等经常使用。</p><p><code>@变量名: 值;</code></p><h3 id="_5-1-变量命名规范" tabindex="-1">5.1 变量命名规范 <a class="header-anchor" href="#_5-1-变量命名规范" aria-hidden="true">#</a></h3><ul><li>必须有 <code>@</code> 为前缀</li><li>不能包含特殊字符</li><li>不能以数字开头</li><li>大小写敏感</li></ul><p><code>@color: pink;</code></p><h3 id="_5-2-基本使用" tabindex="-1">5.2 基本使用 <a class="header-anchor" href="#_5-2-基本使用" aria-hidden="true">#</a></h3><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#676E95;font-style:italic;">// 直接使用</span></span>
<span class="line"><span style="color:#FFCB6B;">body</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">    </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">color</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#FFCB6B;">a</span><span style="color:#89DDFF;">:</span><span style="color:#C792EA;">hover</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">    </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">color</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br></div></div><h3 id="_5-3-变量插值-variable-interpolation" tabindex="-1">5.3 变量插值(Variable Interpolation) <a class="header-anchor" href="#_5-3-变量插值-variable-interpolation" aria-hidden="true">#</a></h3><p>变量用于选择器名、属性名、URL、<code>@import</code>语句</p><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">my-selector</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> banner</span><span style="color:#89DDFF;">;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#676E95;font-style:italic;">// 需要添加 {}</span></span>
<span class="line"><span style="color:#89DDFF;">.</span><span style="color:#A6ACCD;">@{my-selector} </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">font-weight</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> bold</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">line-height</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">40px</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">margin</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">0</span><span style="color:#A6ACCD;"> auto</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br></div></div><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">property</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> color</span><span style="color:#89DDFF;">;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">widget</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  @{property}</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> #0ee</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  background</span><span style="color:#89DDFF;">-</span><span style="color:#A6ACCD;">@{property}</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> #999</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br></div></div><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#676E95;font-style:italic;">// Variables</span></span>
<span class="line"><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">images</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">../img</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#676E95;font-style:italic;">// Usage</span></span>
<span class="line"><span style="color:#FFCB6B;">body</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> #444</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">background</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">url(</span><span style="color:#89DDFF;">&#39;</span><span style="color:#A6ACCD;">@{images}</span><span style="color:#C3E88D;">/white-sand.png</span><span style="color:#89DDFF;">&#39;</span><span style="color:#82AAFF;">)</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br></div></div><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#676E95;font-style:italic;">// Variables</span></span>
<span class="line"><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">themes</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">../../src/themes</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#676E95;font-style:italic;">// Usage</span></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">@import</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#A6ACCD;">@{themes}</span><span style="color:#C3E88D;">/tidal-wave.less</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">;</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div><h3 id="_5-4-延迟加载-lazy-evaluation" tabindex="-1">5.4 延迟加载(Lazy Evaluation) <a class="header-anchor" href="#_5-4-延迟加载-lazy-evaluation" aria-hidden="true">#</a></h3><p>当一个变量被声明多次，会取最后一次的值，并从当前作用域往外寻找变量。</p><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">var</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">0</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">class</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">var</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">1</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">brass</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">    </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">var</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">2</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">    three</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">var</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">    </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">var</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">3</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#A6ACCD;">  one</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">var</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br></div></div><p><strong>编译后</strong></p><div class="language-css line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">class</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  one</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">1</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">class</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">brass</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  three</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">3</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br></div></div><h3 id="_5-5-属性名变量-properties-as-variables" tabindex="-1">5.5 属性名变量(Properties as Variables) <a class="header-anchor" href="#_5-5-属性名变量-properties-as-variables" aria-hidden="true">#</a></h3><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">widget</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> #efefef</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">background-color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> $color</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br></div></div><p><strong>编译后</strong></p><div class="language-css line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">widget</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">#</span><span style="color:#A6ACCD;">efefef</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">background-color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">#</span><span style="color:#A6ACCD;">efefef</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br></div></div><h2 id="_6-嵌套-nesting" tabindex="-1">6.嵌套(Nesting) <a class="header-anchor" href="#_6-嵌套-nesting" aria-hidden="true">#</a></h2><h3 id="_6-1-基本使用" tabindex="-1">6.1 基本使用 <a class="header-anchor" href="#_6-1-基本使用" aria-hidden="true">#</a></h3><p>Less 提供了使用嵌套(nesting)代替层叠或与层叠结合使用的能力</p><p>【我们经常用到选择器的嵌套】</p><div class="language-css line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;">#</span><span style="color:#F78C6C;">header</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">logo</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">    </span><span style="color:#B2CCD6;">width</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">300px</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><p>【less 嵌套写法】</p><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;">#</span><span style="color:#F78C6C;">header</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">    </span><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">logo</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">        </span><span style="color:#B2CCD6;">width</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">300px</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">    </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div><blockquote><p>用 Less 书写的代码更加简洁，并且模仿了 HTML 的组织结构。</p></blockquote><h3 id="_6-2-父选择器-parent-selectors" tabindex="-1">6.2 父选择器 (Parent Selectors) <a class="header-anchor" href="#_6-2-父选择器-parent-selectors" aria-hidden="true">#</a></h3><p>在嵌套规则中， <code>&amp;</code> 表示父选择器，常用于给现有选择器添加伪类。</p><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">header</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#FFCB6B;">a</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">    </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> blue</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">    </span><span style="color:#89DDFF;">&amp;:</span><span style="color:#C792EA;">hover</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">      </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> green</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">    </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br></div></div><p><strong>编译后</strong></p><div class="language-css line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">header</span><span style="color:#A6ACCD;"> </span><span style="color:#FFCB6B;">a</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> blue</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">header</span><span style="color:#A6ACCD;"> </span><span style="color:#FFCB6B;">a</span><span style="color:#89DDFF;">:</span><span style="color:#C792EA;">hover</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> green</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br></div></div><p>你还可以使用此方法将伪选择器（pseudo-selectors）与混合（mixins）一同使用。下面是一个经典的 clearfix 技巧，重写为一个混合（mixin） (&amp; 表示当前选择器的父级）：</p><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">clearfix</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">display</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> block</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">zoom</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">1</span><span style="color:#89DDFF;">;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#89DDFF;">&amp;:</span><span style="color:#C792EA;">after</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">    </span><span style="color:#FFCB6B;">content</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&quot;</span><span style="color:#C3E88D;"> </span><span style="color:#89DDFF;">&quot;</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">    </span><span style="color:#B2CCD6;">display</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> block</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">    </span><span style="color:#B2CCD6;">font-size</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">0</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">    </span><span style="color:#B2CCD6;">height</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">0</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">    </span><span style="color:#B2CCD6;">clear</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> both</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">    </span><span style="color:#B2CCD6;">visibility</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> hidden</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br></div></div><h2 id="_7-混合-mixins" tabindex="-1">7.混合(Mixins) <a class="header-anchor" href="#_7-混合-mixins" aria-hidden="true">#</a></h2><p>混合(Mixin)是一种将一组属性从一个规则集包含(或混入)到另一个规则集的方式，可理解为复制粘贴。</p><h3 id="_7-1-普通混合" tabindex="-1">7.1 普通混合 <a class="header-anchor" href="#_7-1-普通混合" aria-hidden="true">#</a></h3><ol><li>定义了一个bordered类</li><li>如果希望在其它规则集中使用这些属性，只需像下面这样输入所需属性的类（class）名称即可</li></ol><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">bordered</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">border-top</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> dotted </span><span style="color:#F78C6C;">1px</span><span style="color:#A6ACCD;"> black</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">border-bottom</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> solid </span><span style="color:#F78C6C;">2px</span><span style="color:#A6ACCD;"> black</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;">#</span><span style="color:#F78C6C;">menu</span><span style="color:#A6ACCD;"> </span><span style="color:#FFCB6B;">a</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> #111</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#FFCB6B;">.bordered</span><span style="color:#A6ACCD;">()</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">post</span><span style="color:#A6ACCD;"> </span><span style="color:#FFCB6B;">a</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> red</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#FFCB6B;">.bordered</span><span style="color:#A6ACCD;">()</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br></div></div><div class="language-css line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">bordered</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">border-top</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> dotted </span><span style="color:#F78C6C;">1px</span><span style="color:#A6ACCD;"> black</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">border-bottom</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> solid </span><span style="color:#F78C6C;">2px</span><span style="color:#A6ACCD;"> black</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#89DDFF;">#</span><span style="color:#F78C6C;">menu</span><span style="color:#A6ACCD;"> </span><span style="color:#FFCB6B;">a</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">#</span><span style="color:#A6ACCD;">111</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">border-top</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> dotted </span><span style="color:#F78C6C;">1px</span><span style="color:#A6ACCD;"> black</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">border-bottom</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> solid </span><span style="color:#F78C6C;">2px</span><span style="color:#A6ACCD;"> black</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">post</span><span style="color:#A6ACCD;"> </span><span style="color:#FFCB6B;">a</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> red</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">border-top</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> dotted </span><span style="color:#F78C6C;">1px</span><span style="color:#A6ACCD;"> black</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">border-bottom</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> solid </span><span style="color:#F78C6C;">2px</span><span style="color:#A6ACCD;"> black</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br></div></div><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#676E95;font-style:italic;">// 使用类选择器时可以在选择器后边添加一个括号，这时我们实际上就创建了一个mixins</span></span>
<span class="line"><span style="color:#676E95;font-style:italic;">// 这种是不会被识别进css</span></span>
<span class="line"><span style="color:#FFCB6B;">.myMixin</span><span style="color:#A6ACCD;">() </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">width</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">400px</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">height</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">400px</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">p4</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">myMixin</span><span style="color:#89DDFF;">;</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">//.myMixin();都可以</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br></div></div><h3 id="_7-2-带参数的混合-parametric-mixins" tabindex="-1">7.2 带参数的混合(Parametric Mixins) <a class="header-anchor" href="#_7-2-带参数的混合-parametric-mixins" aria-hidden="true">#</a></h3><ol><li>混合带参数，参数需要按顺序传递</li></ol><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#FFCB6B;">.border</span><span style="color:#A6ACCD;">(</span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">width</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">style</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">color) </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">border</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">width </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">style </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">color</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#FFCB6B;">div</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#FFCB6B;">.border</span><span style="color:#A6ACCD;">(</span><span style="color:#F78C6C;">1px</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> solid</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> #ccc)</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br></div></div><div class="language-css line-numbers-mode"><pre><code><span class="line"><span style="color:#FFCB6B;">div</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">border</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">1px</span><span style="color:#A6ACCD;"> solid </span><span style="color:#89DDFF;">#</span><span style="color:#A6ACCD;">ccc</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><ol start="2"><li>混合带参数并有默认值</li></ol><p>需注意的是，就算有默认值，也要按顺序传递</p><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#FFCB6B;">.border</span><span style="color:#A6ACCD;">(</span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">width</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">style</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">#</span><span style="color:#F78C6C;">ccc</span><span style="color:#A6ACCD;">) </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">border</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">width </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">style </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">color</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#FFCB6B;">div</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#FFCB6B;">.border</span><span style="color:#A6ACCD;">(</span><span style="color:#F78C6C;">1px</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> solid)</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#676E95;font-style:italic;">// 会出错</span></span>
<span class="line"><span style="color:#FFCB6B;">.border</span><span style="color:#A6ACCD;">(</span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">width</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">1px</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">style</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">color) </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">border</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">width </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">style </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">color</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#FFCB6B;">div</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#FFCB6B;">.border</span><span style="color:#A6ACCD;">(solid</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> #ccc)</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br></div></div><h3 id="_7-3-命名参数" tabindex="-1">7.3 命名参数 <a class="header-anchor" href="#_7-3-命名参数" aria-hidden="true">#</a></h3><p>可以在向混合传参是指定参数名称，从而不需要按顺序传入</p><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#FFCB6B;">.border</span><span style="color:#A6ACCD;">(</span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">width</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">style</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">#</span><span style="color:#F78C6C;">ccc</span><span style="color:#A6ACCD;">) </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">border</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">width </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">style </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">color</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#FFCB6B;">div</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#FFCB6B;">.border</span><span style="color:#A6ACCD;">(</span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">style</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> solid</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> red</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">width</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">100px</span><span style="color:#A6ACCD;">)</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br></div></div><h3 id="_7-4-arguments-变量" tabindex="-1">7.4 @arguments 变量 <a class="header-anchor" href="#_7-4-arguments-变量" aria-hidden="true">#</a></h3><p><code>@arguments</code> 变量包含了传入的所有参数</p><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#FFCB6B;">.box-shadow</span><span style="color:#A6ACCD;">(</span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">x</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">0</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">y</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">0</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">blur</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">1px</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">#</span><span style="color:#A6ACCD;">000) </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#FFCB6B;">-webkit-box-shadow</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">arguments</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#FFCB6B;">-moz-box-shadow</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">arguments</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">box-shadow</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">arguments</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">big-block</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#FFCB6B;">.box-shadow</span><span style="color:#A6ACCD;">(</span><span style="color:#F78C6C;">2px</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">5px</span><span style="color:#A6ACCD;">)</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br></div></div><div class="language-css line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">big-block</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#FFCB6B;">-webkit-box-shadow</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">2px</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">5px</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">1px</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">#</span><span style="color:#A6ACCD;">000</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#FFCB6B;">-moz-box-shadow</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">2px</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">5px</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">1px</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">#</span><span style="color:#A6ACCD;">000</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">box-shadow</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">2px</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">5px</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">1px</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">#</span><span style="color:#A6ACCD;">000</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div><h3 id="_7-5-匹配模式-pattern-matching" tabindex="-1">7.5 匹配模式(Pattern-matching) <a class="header-anchor" href="#_7-5-匹配模式-pattern-matching" aria-hidden="true">#</a></h3><p>在多个相同的混合中(参数个数必须相同)，匹配特定的混合。</p><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#FFCB6B;">.mixin</span><span style="color:#A6ACCD;">(dark</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">color) </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> darken(</span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">color</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">10%</span><span style="color:#A6ACCD;">)</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#FFCB6B;">.mixin</span><span style="color:#A6ACCD;">(light</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">color) </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> lighten(</span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">color</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">10%</span><span style="color:#A6ACCD;">)</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#676E95;font-style:italic;">// @_ 表示匹配所有</span></span>
<span class="line"><span style="color:#FFCB6B;">.mixin</span><span style="color:#A6ACCD;">(</span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">_</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">color) </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">display</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> block</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">switch</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> light</span><span style="color:#89DDFF;">;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">class</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#FFCB6B;">.mixin</span><span style="color:#A6ACCD;">(</span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">switch</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> #888)</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br></div></div><div class="language-css line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">class</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">#</span><span style="color:#A6ACCD;">a2a2a2</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">display</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> block</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br></div></div><h3 id="_7-6-运算-operations" tabindex="-1">7.6 运算(Operations) <a class="header-anchor" href="#_7-6-运算-operations" aria-hidden="true">#</a></h3><p>任何数字、颜色或者变量都可以参与运算。就是 Less 提供了加（+）、减（-）、乘（*）、除（/）算术运算。</p><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#676E95;font-style:italic;">/* Less 里面写 */</span></span>
<span class="line"><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">width</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">10px</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">+</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">5</span><span style="color:#89DDFF;">;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#FFCB6B;">div</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">    </span><span style="color:#B2CCD6;">border</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">width solid red</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#676E95;font-style:italic;">/* Less 甚至还可以这样 */</span></span>
<span class="line"><span style="color:#FFCB6B;">width</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> (</span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">width </span><span style="color:#89DDFF;">+</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">5</span><span style="color:#A6ACCD;">) </span><span style="color:#89DDFF;">*</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">2</span><span style="color:#89DDFF;">;</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br></div></div><p>【生成的 css】</p><div class="language-css line-numbers-mode"><pre><code><span class="line"><span style="color:#FFCB6B;">div</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">    </span><span style="color:#B2CCD6;">border</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">15px</span><span style="color:#A6ACCD;"> solid red</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><p>注意：</p><ul><li>乘号（*）和除号（/）的写法要牢记</li><li>运算符中间左右必须有个空格隔开 <code>1px + 5</code></li><li>在新版本的 Less 中，除法有变动，应将 <code>100px / 10</code> 改为 <code>(100px / 10)</code>，否则没有效果</li><li>对于两个不同的单位的值之间的运算，运算结果的值取第一个值的单位</li><li>如果两个值之间只有一个值有单位，则运算结果就取该单位</li></ul><p>计算结果以操作数最左侧的单位类型为准</p><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">conversion-1</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">5cm</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">+</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">10mm</span><span style="color:#89DDFF;">;</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">// 6cm</span></span>
<span class="line"><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">conversion-2</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">2</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">-</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">3cm</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">-</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">5mm</span><span style="color:#89DDFF;">;</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">// -1.5cm</span></span>
<span class="line"><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">conversion-3</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">3.1</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">*</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">2cm</span><span style="color:#89DDFF;">;</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">// 6.2cm</span></span>
<span class="line"><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">conversion-4</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">4px</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">/</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">2</span><span style="color:#89DDFF;">;</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">// 4px / 2</span></span>
<span class="line"></span>
<span class="line"><span style="color:#676E95;font-style:italic;">// conversion is impossible</span></span>
<span class="line"><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">incompatible-units</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">1cm</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">-</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">1px</span><span style="color:#89DDFF;">;</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">// 0.97354167cm</span></span>
<span class="line"></span>
<span class="line"><span style="color:#676E95;font-style:italic;">// example with variables</span></span>
<span class="line"><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">base</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">5%</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">filler</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">base </span><span style="color:#89DDFF;">*</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">2</span><span style="color:#89DDFF;">;</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">// 10%</span></span>
<span class="line"><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">other</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">base </span><span style="color:#89DDFF;">+</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">filler</span><span style="color:#89DDFF;">;</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">// 15%</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> #224488 </span><span style="color:#89DDFF;">/</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">2</span><span style="color:#89DDFF;">;</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">// #112244</span></span>
<span class="line"><span style="color:#FFCB6B;">background-color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> #112244 </span><span style="color:#89DDFF;">+</span><span style="color:#A6ACCD;"> #111</span><span style="color:#89DDFF;">;</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">// #223355</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br></div></div><h2 id="_8-继承-extend" tabindex="-1">8.继承(Extend) <a class="header-anchor" href="#_8-继承-extend" aria-hidden="true">#</a></h2><p>Extend Syntax</p><ul><li>继承可让多个选择器应用同一组属性，最终编译为并集选择器</li><li>其性能比混合高，但灵活性比混合低</li></ul><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#FFCB6B;">nav</span><span style="color:#A6ACCD;"> </span><span style="color:#FFCB6B;">ul</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#89DDFF;">&amp;:</span><span style="color:#A6ACCD;">extend(</span><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">inline</span><span style="color:#A6ACCD;">)</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">background</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> blue</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">inline</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> red</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br></div></div><div class="language-css line-numbers-mode"><pre><code><span class="line"><span style="color:#FFCB6B;">nav</span><span style="color:#A6ACCD;"> </span><span style="color:#FFCB6B;">ul</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">background</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> blue</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">inline</span><span style="color:#89DDFF;">,</span></span>
<span class="line"><span style="color:#FFCB6B;">nav</span><span style="color:#A6ACCD;"> </span><span style="color:#FFCB6B;">ul</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> red</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br></div></div><h3 id="_9-避免编译" tabindex="-1">9.避免编译 <a class="header-anchor" href="#_9-避免编译" aria-hidden="true">#</a></h3><p>通过加引号可以避免 Less 编译，直接把内容输出到 CSS 中</p><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">banner</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">inline</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">header</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">width</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">100px + 100px</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">height</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">100px</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">+</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">100px</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br></div></div><div class="language-css line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">banner</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">inline</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">header</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">width</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&#39;</span><span style="color:#C3E88D;">100px + 100px</span><span style="color:#89DDFF;">&#39;</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">height</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">200px</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br></div></div><h2 id="_10-函数（functions）" tabindex="-1">10.函数（Functions） <a class="header-anchor" href="#_10-函数（functions）" aria-hidden="true">#</a></h2><p>Less 内置了多种函数用于转换颜色、处理字符串、算术运算等。这些函数在Less 函数手册中有详细介绍。</p><p>函数的用法非常简单。下面这个例子将介绍如何利用 percentage 函数将 0.5 转换为 50%，将颜色饱和度增加 5%，以及颜色亮度降低 25% 并且色相值增加 8 等用法：</p><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">base</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> #f04615</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">width</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">0.5</span><span style="color:#89DDFF;">;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">class</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">width</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">percentage</span><span style="color:#A6ACCD;">(</span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">width)</span><span style="color:#89DDFF;">;</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">// returns `50%`</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">saturate</span><span style="color:#A6ACCD;">(</span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">base</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">5%</span><span style="color:#A6ACCD;">)</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;">  </span><span style="color:#B2CCD6;">background-color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#82AAFF;">spin</span><span style="color:#A6ACCD;">(lighten(</span><span style="color:#89DDFF;">@</span><span style="color:#A6ACCD;">base</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">25%</span><span style="color:#A6ACCD;">)</span><span style="color:#89DDFF;">,</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">8</span><span style="color:#A6ACCD;">)</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br></div></div><h2 id="_11-导入（importing）" tabindex="-1">11.导入（Importing） <a class="header-anchor" href="#_11-导入（importing）" aria-hidden="true">#</a></h2><p>你可以导入一个 .less 文件，此文件中的所有变量就可以全部使用了。如果导入的文件是 .less 扩展名，则可以将扩展名省略掉：</p><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#89DDFF;font-style:italic;">@import</span><span style="color:#A6ACCD;"> url(</span><span style="color:#89DDFF;">&quot;</span><span style="color:#C3E88D;">syntax.less</span><span style="color:#89DDFF;">&quot;</span><span style="color:#A6ACCD;">)</span><span style="color:#89DDFF;">;</span><span style="color:#676E95;font-style:italic;">//url可以不加但是可能会有问题</span></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">@import</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&quot;</span><span style="color:#C3E88D;">library</span><span style="color:#89DDFF;">&quot;</span><span style="color:#89DDFF;">;</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">// library.less</span></span>
<span class="line"><span style="color:#89DDFF;font-style:italic;">@import</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&quot;</span><span style="color:#C3E88D;">typo.css</span><span style="color:#89DDFF;">&quot;</span><span style="color:#89DDFF;">;</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><h2 id="_12-导出" tabindex="-1">12.导出 <a class="header-anchor" href="#_12-导出" aria-hidden="true">#</a></h2><p><strong>手动给每个less文件指定导出</strong></p><p>导出必须写到第一行</p><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#676E95;font-style:italic;">// out: 路径/文件名</span></span>
<span class="line"><span style="color:#676E95;font-style:italic;">// out: ./mycss/pink.css</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br></div></div><p>设置导出： 当面目录下，创建一个 mycss 文件夹， 生成 一个 pink.css （做了改名）</p><hr><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#676E95;font-style:italic;">// out: ./mycss/</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br></div></div><p>设置导出： 当面目录下，创建一个 mycss 文件夹， 生成 一个 跟less一样的文件名（原名）</p><p><strong>less 禁止导出</strong></p><div class="language-less line-numbers-mode"><pre><code><span class="line"><span style="color:#676E95;font-style:italic;">// out: false</span></span>
<span class="line"></span></code></pre><div class="line-numbers-wrapper"><span class="line-number">1</span><br></div></div></div></div><!----></main><!--[--><!--]--><!----></div></div></div></div><div class="visually-hidden" aria-live="polite" data-v-23306c50>Less基础 has loaded</div></div></div>
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